DE2917889A1 - FILTER CANDLE - Google Patents

Description

PATENT LAWYERS

WUESTHOFF - ν. PECHMANN - BEHRENS - GOET2

PROFESSIONAL REPRESENTATIVES BEFORE THE EUROPEAN PATENT OFFICE MANDATAiRES agrees pres l'opfice europeen des brevets DÄ.-ING. FRANZ WUESTHOFF DR. PHIL. FREDA WUESTHOFF (1927-I956) DIPL.-ING. GERHARD PULS (1952-1971) DIPL.-CHEM. DR. E. BARBER OF PECHMANN DR.-ING. DIETER BEHRENS DIPL.-ING .; DIPL.-WIRTSCH.-ING. RUPERT GOETZ

D-8000 MÜNCHEN 90 SCHWEIGERSTRASSE 2 phone: (089) 66 20 51 telegram: protectpatent telex: 514070

1A-52 038

Patent application

Applicant: ECODYlCE CORPORATION

90 Half Day Road, Lincolnshire, Illinois 60015, U.S.A.

Title:

Filter candle

S09846 / 0707

DR.-I NG. FRANZ VUESTHOFF

PATENTANWÄLTE _{DR> PHIL} , _F reda wuesthoff (1927-1956)

WUESTHOFF -ν. PECHMANN -BEHRENS -GOETZ d.fwno.geshard puls (195 ^ 970

DIPL.-CHEM. DR. E. BARBER OF PECHMANN PROFESSIONAL REPRESENTATIVES BEFORE THE EUROPEAN PATENT OFFICE DR.-ING. DIETER BEHRENS

MANDATAIRES AGREES PRES l'OFFICE EUROPEEN DES BREVETS DIPL.-ING .; DIFL.-WIRTSCH.-ING. RUPERT GOETZ

D-8000 MUNICH 90 SCHWEIGERSTRASSE 2

phone: (089) 66 20 ji

o telegram: protectpatent

telex: j24070

1A-52 038 Description:

The invention relates to a filter candle for use in a filter container for cleaning liquids. The invention is aimed at reducing the gas flow in of the filter candle during the precoat on an inlet side Precoat layer of granular filter aid and during of the subsequent filter operation.

It is known to purify liquids by passing them through a filter candle covered with a precoat of ion exchange resin particles in the grain size range from 260 to 37 μm (US Pat. No. 3,250,703).

In such a system, a large number of filter candles are usually arranged vertically in a filter container. These known filter candles v / iron a core made of stainless steel, which is provided with perforations or openings, and a coarse wire screen is placed around the core, which in turn is surrounded by a layer of a fine-meshed wire screen and the support of the precoat layer serves. The precoat from the filter aid becomes tapered deposited on the side of the filter candles by adding an aqueous. Slurry the filter aid particles through the filter canister is directed. The length of these filter cartridges is due to the expense of the corrosion-resistant filter cartridge parts and the The size of the container used for the filtering process is limited Can be, because of this size limit it is

(a

eririinscht, the entire filter candle with the filter aid to cover.

During the filling of the filter container with liquid for the purpose of depositing the precoat layer or for initiating the filter operation however, a certain amount of air or other gases will accumulate in the upper part of each filter candle and trapped there as a result of capillary action. When the tiny openings or pores of the filter candle from the liquid are moistened in the filter container, an interface is created between the liquid, air or other gases in the filter container and the wall surfaces of each screen of the wire screen on which the filter aid is deposited. The surface tension the liquid across the pores creates a force which must be overcome so that gas can pass through the pore can. The resulting gas pressure in the pore, which is in equilibrium with the surface tension force generated by capillary action is in the largest pore of a filter candle, is referred to as bubble point pressure - according to Aerospace Recommended Practice (ARP) 901 of the Society of Automotive Engineers, Inc .. The lower the bubble point pressure of a given If the filter candle is, the lower the likelihood of gas leakage during precoating or filtering is enclosed in a filter candle.

It is known that this trapped gas is at least has an adverse effect in two respects. Firstly, the trapped gas prevents the filter aid suspension from flowing through and thus a flooding in the area of those surfaces of the filter candles in which the gas is present, creating areas are created without a precoat layer through which the liquid with impurities can pass through the filter candle can. Second, the presence of trapped gas leads to a periodic one during the filtering phase The gas escapes to the outside through the filter candle, causing areas of the precoat layer to tear or even be removed can.

/ 3 909846/0707

The problem of gas inclusions in filter cartridges is particular Significance for filter candles with an absolute particle retention capacity of less than 50 μm and with a precoat layer made of filter aid that has a low pressure drop during filter operation, such as for powdery ion exchange resins in the grain size range of 37 to 260 µm or below. The absolute particle retention capacity is the largest dimension of the smallest particle that is always retained by the filter candle, and they is therefore due to the smallest dimension of the largest pore Filter candle determined. Various attempts to solve the problem of gas accumulation or gas influences have become known, for example, U.S. Patents 3,630,700 and 3,779,386.

In the known filter candles, a considerable volume of trapped gas collects at the top of each candle. Are the filter candles in a filter container with a lower ear plate between the upper inlet chamber and the lower inlet chamber arranged, the gas is trapped in the core of the filter element. Is the filter canister with an upper one If the tube sheet is provided, the gas is retained on the outside of each filter candle. The outer surface of everyone The filter candle is not covered with the precoat in the area of the enclosed gas volume. If the pressure increases in the Filter container over the pressure when precoating, the enclosed gas volume is compressed and / or the capillary force exceeded and uncleaned liquid flows through the exposed areas of the filter cartridge that are free of alluvial layers. The pressure in the filter container increases in three cases in particular: First when the filter starts operating, then when Occurrence of flow oscillations or flow surges during the filtering and finally after the build-up of a noticeable filter cake of undissolved impurities. That Flow of uncleaned liquid through the exposed areas of the filter cartridges can clog the cartridges due to solid particles contained in the water or to the premature termination of the filtering phase as a result of their presence of impurities in the filtrate emerging from the filter container. 909846/0707

Attempts to solve the problem of gas inclusions have already been referred to. For example is U.S. Patent Nos. 3,680,700 and 3,799,386 show a precoat Filter candle known, which at its upper end by a dome-shaped Cover or vent sleeve is surrounded. The cover is provided with a vent that communicates with the inner area of the filter cartridge. This training If a filter aid is used in the grain size range from 37 to 260 μm, it can be used

however, they cannot be used effectively with filter cartridges that have low absolute particulate hold-up without substantial changes to the apparatus. If an absolute particle retention capacity of 50 μm or less is required and a fine-meshed wire mesh is used for this, the filter candle in question becomes uneconomical because of the cost of material for the necessary ventilation sleeve and because of the reduction in the effective filter surface of the filter candle because of the length of the ventilation sleeve. This reduction results from the critical length in the dimensioning of the venting sleeve, which is determined by the height of the enclosed gas volume which is present after the filling of liquid into the filter container if no venting sleeve is provided. This height of the enclosed gas volume is measured as the perpendicular distance from the gas-liquid contact surface to the highest exposed area of the layer supporting the filter aid at the top of the filter candle, and this height is proportional to the bubble point pressure of the filter candle layer which has the highest bubble point pressure, which is usually is the outermost layer that supports the filter aid.

Other attempts that have become known to solve the problem of gas inclusions involve the addition of a surface-active agent Means to reduce the surface tension of the liquid and. a complete drying of the filter candles before Fill with liquid to remove the liquid which is causing the surface tension forces across the filter candle pore

909846/0707 / 5

evokes. However, the addition of a surfactant does not provide an acceptable solution to the problem dax * because of it an unacceptable level of foaming is produced and the addition of such chemical agents to the liquid to be purified is often undesirable. A complete drying of the filter candles before filling with liquid is prevented Although gas influences, it requires a considerable period of time, which increases the downtime of the filter system and the amount of time available for filtering is reduced.

In a preferred embodiment of the invention is a Filter candle provided, which can be coated with a precoat layer of a filter aid and the one porous ■ tubular core as well as a support for the Has precoat layer which has a jacket with discontinuous slots concentric around the tubular Core is arranged around. The bubble point pressure of the filter candle is reduced under the pressure of a known one Filter candle would be expected, which has a corresponding absolute particle retention capacity, and thereby the connection of gas is reduced.

While in the known designs the layers to support the filter aid consist of a fine sieve or mesh, which is arranged concentrically over a coarse drainage sieve, which in turn surrounds a central tubular core, according to the invention the fine-meshed sieve is replaced by a jacket with discontinuous slots. Each of the slots has an elongated shape, with "the slot width is chosen such that the desired absolute Teilchenzurückhaltefähigkeit is achieved that is preferably less than 50 / microns. The length of the slots is chosen such that the bubble point pressure significantly over a comparable fine Sieve mesh is reduced, which has an absolute particle retention capacity of

•. / 6

Ate

is less than 50 µm, this will reduce the amount of in reduced gas trapped in the filter candle.

In another preferred embodiment of the invention, a filter candle is provided which is provided with a precoat layer can be provided from a filter aid and a porous tubular core and a support for the Has deposited filter aid, which is arranged around the tubular core and at a distance from one End of the tubular core ends, so that a filter candle portion is formed which has a comparatively low Has bubble point pressure. The filter candle also has a

Jacket with discontinuous slits, which is in the area of the section with comparatively low bubble point pressure extends around the tubular core and with the Support for the precoat is connected.

Another preferred embodiment is with a vent sleeve provided, which is arranged over the slotted jacket and connected to it and has an opening on v / eist, which is covered by the slit jacket. Alternatively, the slotted jacket is under the opening of the venting sleeve arranged but does not extend circumferentially around the tubular core, and the vent sleeve is sealingly connected with the support for the precoat layer. These designs achieve the advantage of degradation the inclusion of gas in the filter candle due to a low bubble point pressure on a section of the filter candle, on which a surface for gas release is provided through a discontinuously slotted jacket. This section is so arranged in the filter container that the maximum driving force of the gas to expel acts on this section.

In the preferred embodiments, the slotted jacket is preferably adhered by diffusion bonding or penetration on the adjacent parts of the filter cartridge where there is

/ 7 909846/0707

is usually a layer of coarse wire mesh. In particular in the embodiment with a slotted jacket, which acts as an outer layer over the entire length extending the filter candle, this sticking leads to several disadvantages. There are numerous contact points or adhesive points between the slotted jacket and the coarse wire screen, eliminating the possibility of the slotted jacket during an increase or a reversal of the liquid flow and force and the resulting resul- ' tensions and tensile stresses on the slit jacket ice is reduced. Furthermore, the mutual penetration at different contact points leads to a substantial one. Support of the slot jacket and to reduce the possibility of widening of the slots by physical impact in comparison with a fine-mesh wire screen with a corresponding absolute particle retention capacity.

The embodiment according to the invention with a slot jacket extending over the entire length of the filter candle Supporting the precoat layer avoids the disadvantages of the known filter candles Filter candle is significantly reduced, in particular the bubble point pressure of the outer layer of the filter candle, which is in the generally has the greatest bubble point pressure and therefore the crucial layer in the regulation of the bubble point pressure is. With the help of the discontinuously slotted outer jacket layer of the filter candle, a retention of Particles of a size of less than 50 / um achieved while at the same time a filter candle is created that has a low resistance to the flow of gas even when it is wet opposed. The filter candle has a retention of particles that is less than that of a filter candle Use of fine-meshed wire mesh as a cladding is the same, but with a better ability to release Gas compared to the filter candles using fine-mesh wire mesh to achieve the same absolute Particle retention is present.

909846/070? /8th

Furthermore, the inventive training with a discontinuous Outer jacket having slits is less prone to irreversible clogging than filter candles with a wire mesh cover of corresponding absolute particle retention capacity.

The advantages of the filter candle according to the invention lead to that the costs of a filter system with a certain effective filter surface are reduced, since more filter candle surface can be effectively provided with a precoat from the filter aid and used during the filter phase can be.

Several exemplary embodiments of the invention are explained in more detail below with reference to a schematic drawing. It shows:

Fig..1 is a partially sectioned view of a filter container with cylindrical filter candles in accordance with the invention Education;

2 shows a perspective, partially cut-away illustration of the upper end of a first embodiment of the filter candle with a central core, a coarse one Sieve layer, a jacket with discontinuous slots as a support for the precoat layer and a vent sleeve;

3 shows, in a representation corresponding to FIG. 2, a modified embodiment with a slit jacket extending only over the height of the ventilation sleeve; and

Fig. 4 in a Fig. 2 and j? corresponding representation further modified embodiment in which the slit jacket is only in the area of the ventilation openings the ventilation sleeve extends.

/ 9 909846/0707

In Pig. 1, a filter system is illustrated _t is known from US-PS corresponds 3279608 "known plant and having a filter Lieh Older 10, which is introduced liquid to be filtered in the in which the liquid is filtered and from which flows the filtrate..

The filter container 10 is a cylindrical vessel made of steel or the like. With a convex outwardly bulging cover part 11 and an outwardly convexly protruding bottom part 13. The container 10 is bent downward by a Tube sheet 17, which is welded to the inside of the container 10, into an inlet chamber 15 and a filtrate chamber 15 divided. The feed line 12 extends through the bottom part 13 of the container and stands with der.Zulaufkammer 15 in connection, so that the entire feed is passed directly into the feed chamber 15. The feed line 12 is with the Tube sheet 17 connected by welding. In this way is a direct connection between the inlet chamber 15 and the filtrate chamber 16 switched off.

In the inlet chamber 15 there are many filter candles 18 through which the inlet must flow before it enters the filtrate chamber 16 and exits the container 10 through the outlet line 14. The filter candles 18 iron according to the invention a reduced bubble point pressure, which is indicated by a discontinuous slotted jacket 86 is achieved, as shown in FIG. Alternatively, the filter candles 18 can also be designed as. it in Fig. 3 or 4 is shown. Each filter candle 18 is in its vertical position in the inlet chamber 15 of the filter container 10 held by a holding arrangement 20. This holding arrangement 20 is a centering pin 94 on a cover 90 on, which is shown in Fig. 2 to 4, and holds the filter candle releasably in position on a filter seat 30, which with the Tube sheet 17 is connected. The filter candles 18 are inserted into the container through a small manhole opening 22 in the filter container 10 introduced and removed from it. The manhole opening 22

/ 10 909846/0707

is provided with a lid 24 which can be removed if desired or opened v / erdenk can to make the interior of the filter container 10 accessible.

The filter container 10 is provided with a vent 26 and with a reserve connection 28, which in the present case is locked. The design of the vent 26 is dependent on the use of the filter canister, the special training is familiar to the specialist.

The filter seats 30 consist of a small tube made of steel or the like. Which extends through a hole in the tube sheet Ψ and is welded to this. Each filter seat 30 extends essentially parallel to the longitudinal axis of the filter container 10 and creates a connection between the inlet chamber 15 and the filtrate chamber 16. Each filter seat 30 forms a support base for a filter candle 18, which is held in position on the seat 30 by the holding arrangement 20 .

A filter candle 13 according to a preferred embodiment of the invention is shown in detail in FIG. This candle 18 has a tubular support core 82, a layer of coarse wire mesh 84, which concentrically around the Support core 82 is arranged around, and an outer layer in the form of a metal jacket provided with discontinuous slots 86, which is arranged concentrically around the coarse wire screen 84 and adheres to this and serves to the Filter aid in the form of finely divided synthetic resin particles, usually in the grain size range from 37 to 260 μm or smaller to support. The tubular support core 82 is designed to be porous and, as shown in FIG Perforations may be provided as a core made of wound fibrous or compacted granular material (not shown) be executed or otherwise be made liquid-permeable. The tubular support core 82 is preferred made of stainless steel and provided with a large number of symmetrically spaced openings,

909846/0707

-μ-

to form about 20 % open area on the outer circumferential surface of the support core 82. The preferred range of the percentage of open area or perforation area of the support core 82 is from 5 % to 65 % _f and the inner diameter of the support core 82 is preferably between 1.9 and 6.3 cm.

The layer of coarse wire screen 84 serves to support the outer layer 86 provided with the slots and to distribute the liquid flow between the slot jacket 86 and the. Support core- 82. That. Wire screen 84 is sized so that it does not significantly affect the bubble point pressure of the filter candle. In the preferred embodiment, the coarse screen 84 has a mesh size of about 150 μm. The limiting or determining component for the value of the bubble point pressure of the filter candle 18 is the outer estimated jacket layer 86. This jacket is made from a suitable metal, preferably from a nickel sheet about 0.05 mm thick, which can be provided with rectangular slots 88 which has a width of about 30yum and a length of about. 430 / µm. The slot jacket 86 is arranged with dimensional stability, so that each slot 88 extends with its longitudinal direction in the circumferential direction of the filter candle 18, as is shown in FIGS. 2, 3 and 4.

Although the slots 88 are shown to be rectangular in shape, they can also be oval or any elongated shape, a slit width is provided which gives the cladding 86 a uniform, absolute particle backward ability confers. The length of a slot 88 is at least about one and a half times its smallest dimension, whereby a large slot cross-sectional area results xuid a lower one Bubble pressure is promoted while the desired design of the absolute particle retention capacity for small particle sizes is achieved. It has been shown that in a case in which the slot length is significantly greater than the slot width is the bubble point pressure of such a slot itself approaches half the bubble point pressure of a circular pore,

_{90984670707/12}

whose diameter corresponds to the width of the slot. For a slot with a width of 30 µm, the length is of the slot is preferably at least 45 µm.

However, the length of each slot cannot be so great that the width dimension has the required tolerance loses, as is the case when each slot actually loses a continuous opening around the perimeter of the candle 18 is. Since the extent of the gas inclusion in a cylindrical filter candle 10 with the bubble point pressure of the filter layer 86 increases, is the gas inclusion that with the slot jacket 86 provided filter candle 18 occurs, less than with a corresponding filter candle that has a filter layer which has circular pores or capillary openings with the same absolute particle retention capacity.

As shown in Fig. 2, the filter cartridge 18 also has a Dome-shaped cover or vent sleeve 90 on which the upper Part of the filter candle 18 closes. At least one vent 92, preferably three or four vents are provided, extends through the top portion of the ventilation sleeve 90, so that a flow connection between the interior of the filter candle 18 and the outer surface the filter candle 18 consists. Although according to FIGS. 2, 3 and 4, the openings 92 in the cylindrical side wall of the Ventilation sleeve 90 are arranged, one or more openings can also be in der.oberen end face of the ventilation sleeve 90 can be provided and lead to the desired results if a slot jacket 86, 96 or 98 is used. In the In the preferred embodiment according to FIG. 2, the support core 82, the coarse screen 84 and the slot jacket 86 each extend upward beyond the vents 92. The purpose the vent sleeve 90 is to prevent the Trapped gas comes into contact with the surface of the filter cartridge 18 coated by the filter aid, whereby this Alluvial surface in the embodiment according to FIG

909846/0707 ^{/ 13}

is formed by the slot jacket 86 and, in FIGS. 3 and 4, by the fine-mesh screen 102.

If the ventilation sleeve 90 is correctly designed, a Gas-liquid contact surface at the bottom of the venting sleeve 90 after the container 10 has been filled with liquid, and the presence of this interface below the vent sleeve 90 prevents gas from touching the surface of the filter candle 18 that can be coated with a precoat layer. The pressure in the filter container 10 rises, as it does during the precoat is the case, the gas is compressed, the gas-liquid interface moving upward and continuing ensures that gas does not come into contact with the surface of the filter candle 18 on which the precoat is to be deposited is.

The critical length A for dimensioning the venting sleeve 19 is equal to the height of the volume of enclosed gas that after the water filling would be present if there was no ventilation sleeve 90 would be used. The critical length A is measured as the perpendicular distance of the gas-liquid interface to the highest exposed slots on the top End of the filter element 18, and this distance is proportional to the bubble point pressure of the slot jacket 86. The gas-liquid interface forms within the tubular support core in the case of filter candles which are arranged in a filter container 10 are, which has a tube sheet 17, as shown in Fig. is shown and the interface occurs at the container side the filter candles on when a (not shown) upper Tube sheet is used as is known in the art.

The term bubble point pressure used here is used after the aforementioned procedure ARP 901 of March 1, 1968 determined. In order to use the To obtain bubble point pressure, the filter element is first immersed in the test liquid to restore its pore cone structure moisten and saturate. Gas pressure is applied to the Inside of the filter element so that liquid,

809846/0707 / ¹⁴

which has moistened the filter element, is displaced by the gas. The gas pressure is slowly increased until the first steady stream is observed by gas bubbles emerging at one point on the filter element. The bubble point pressure is defined as the measured gas pressure required to form the first bubble released from the filter element, and The bubble point pressure is essentially equal to the compressive force which is in equilibrium with the surface tension force at the largest opening in the outer filter element layer.

In the preferred embodiment of the invention shown in FIG. 3, the filter candle comprises a discontinuous one Slotted jacket tape 96, which is arranged below the ventilation sleeve 90, The jacket tape 96 is with the the same preferred slot dimensions, material, construction and other limitations as the protective jacket 86. However, the filter precoat is over the exposed Length of the filter candle 18 supported by a fine-meshed screen mesh 102, which is around the coarse screen 84 and the Support core 82 is arranged. As shown in FIG. 3, the fine-mesh screen 102 ends at a distance from the upper end of the tubular core 82, so that a filter candle section is formed which has a bubble point pressure which is determined by the coarse screen 84 and accordingly relatively low im Compared to the fine-mesh screen 102 is. The slit jacket tape 96 with the lower bubble point pressure than the fine-mesh screen 102, but with a greater bubble point pressure as the coarse screen 84 is positioned and sealingly over the filter element portion of relatively low bubble pressure connected to the fine-mesh sieve 102 at point B by welding or in some other way to create a passage Prevent liquid from flowing through the filter cartridge 18 without cleaning the filter. The vent sleeve 19 is above the with Slit provided jacket tape 96 arranged and with this

connected in a suitable manner in order to also prevent liquid without a cleaning effect from flowing through the filter candle flows. As shown in Figure 3 are the vents 92 of the vent sleeve 90 from a portion of the slotted

909846/0707 _{/ 15}

provided jacket tape 96 covered, and included Gas is released from the filter candle 18 through the slit jacket band 96 with the relatively low bubble pressure and the ventilation openings 92 released. The dimensions of the slots in the belt 96 are chosen to provide absolute particle retention results, which corresponds to that of the fine-meshed screen 102, so that impurities that are on the slit jacket tape 96 meet through this do not flow through.

In the embodiments according to FIGS. 2 and 3, it was found that, depending on the parameters of the filter candle 18 and the filter container 10 no air in the filter candle 18 was included, as shown in the example below II is explained. Under these circumstances, the critical length A for the ventilation sleeve 90 can be reduced significantly, and the design of the vent sleeve 90 is changed so that it acts only as a lid, as would be known to those skilled in the art is, the release of the gas through the slotted jacket 86 or the slotted jacket tape 96 takes place.

According to a further preferred embodiment of the Invention, which is shown in Fig. 4, the fine-mesh screen 102, the coarse screen 84 and the support core 82 as in the embodiment according to FIG. 3 arranged. However, there is a discontinuous slotted jacket washer 98 directly under the openings 92 by tack welding, Diffusion adhesion or otherwise connected to the vent sleeve 90, creating a component with relatively low bubble pressure arises, which serves to release trapped gas and at the same time impurities that happen to be in the vent 92 get back through the slotted jacket disc. Hence the 'slot dimensions of the shell disc 98 selected so that the jacket disc 98 has an absolute particle retention capacity - that of the fine-meshed Sieve 102 is the same. Furthermore, the ventilation sleeve 90 is welded to the fine-mesh screen 102 or otherwise connected at point C. The slits of the coat

809846/0707 / 16

The washers 98 are designed as set forth with respect to the slots in the shell 86 and are the preferred material construction and other limitations of the slot jacket 86 also apply to the jacket disk 98 provided with slots.

In particular in the preferred embodiments according to FIGS. 2 and 3, it is provided that the slot jacket 86 and the slit jacket band 96 with the coarse wire screen through a Diffusion bonding processes are connected at numerous points on the jacket 86 or tape 96. However, since the Schiitz strap 96 is arranged below the ventilation sleeve 90, other suitable methods of connection can also be used for this embodiment and seal in place. For use with a slit jacket 86 or slit band 96 made of nickel and a coarse screen 84 made of corrosion-resistant steel, the method of diffusion bonding is preferred, and sometimes it is is referred to as sintering and consists in that the jacket 86 or the band 96 against the coarse screen 84 in a hydrogen atmosphere or under vacuum, the material temperature being brought to about 1093 ° C for a period of time causing diffusion or particles between the jacket 86 or the belt 96 and the coarse screen 84 cause clinging.

When operating the system shown in Fig. 1 is a liquid Slurry containing the filter aid for the precoat layer, in the present case finely divided ion exchange resin in the grain size range from about 37 to 20 / µm or smaller stored in a precoat tank 32. A line 34 with a Valve 36 connects the precoat tank with a pump 38..A transport line 40 connects the pump 38 with the Feed line 12 of the filter container 10. In the transport line A valve 42 is arranged near the pump 38 and controls the passage of the aqueous slurry from the pump 38.

/ 17 909846/0707

2917888

The liquid to be treated passes through a supply line 44 with a valve 46. The feed line 44 opens into the transport line 40 between the valve 42 and the feed line 12 *

The outlet line 14 from the filter container 10 is at a T-connection 52 with an operating line 48 and a precoat return line 50 connected "The service line 48 is connected to consumers (not shown)", for example a steam generator or the like, and is provided with a valve 54. The precoat return line 50 is with the precoat tank 32 connected and with a return valve 56 for Control of the flow of the slurry back to the precoat tank 32 is provided.

A bridge line 58 with a valve 60 connects the precoat return line 50 with line 34 “A drain line 62 with a valve 64 is connected to the feed line 12.

During the start-up phase, a precoat layer is formed finely divided ion exchange resin particles deposited on the inlet side on the filter candles 18, that is to say on the sides on which the liquid is introduced into the filter candles 18. Accordingly, a filter cake is created inside during the filter phase and built up on the inlet side of the precoat layer.

When preparing the filter system for operation, the first step is to precoat the filter aid onto the Filter candles 18. For this purpose, the container 10 is filled with water of less Contamination like demineralized water filled «A slurry from the filter aid or precoat material and Demineralized water is produced in the precoat tank 32, with the precoat material being finely divided granularly ™ ge ion exchange resin is »

/ 18 909846/0707

3,%

During the precoat all valves are closed with Except for valves 36,42,56 and 60. The precoat will initiated by starting the pump 38, whereby the precoat sucked out of the precoating container 32nd and through the line 34 of the pump 38 is supplied. The pulp is by means of the pump 38 through the transport line 40 and through the feed line 12 pressed into the filter container 10. The pressure of the inflowing pulp displaces the demineralized water in the filter container through the filtrate chamber 16 and the outlet line 14. Some of the demineralized water passes through the return line 50 into the precoat tank 32, and a second part is through the bridge line 58 of the line 34 supplied.

As the circulation progresses, the debris is added to the plant brought to the inlet-side surfaces of the filter candles 18. The fine plastic particles of the precoat material are separated from the paste and form a precoat layer on the inlet side Surfaces of the filter candles 18 deposited. The pulp is circulated through the filter system in the manner described above, until a sufficiently thick precoat layer is on the Filter candles 18 is deposited. The precoating process is thereby ends with valves 36 and 56 closed. Then the filter system is ready to be used to treat feed water or liquid. The strenght the precoat layer on the slit jacket 86 is not critical, but preferably the layer is one Thickness in the range from about 1.6 to 51 mm, with a narrower range between about 3.2 and 25.4 mm and a narrower range Range of about 3.2 to 15.9 mm are particularly preferred.

The operating phase or filter phase is initiated in that the valves 54 and 46 are opened. This is untreated Liquid supplied to the filter system through the supply line 44 and flows through the transport line 40 and the Inlet line 12 into the filter container 10. The pressure of the inflowing untreated liquid pushes it through

909846/0707 ^{/ 19}

Precoat layer, the filter candles 18 and the filtrate chamber 16 into the outlet line 14. After the formation of this operating flow, the valves 42 and 60 are closed and the pump 38 switched off.

When the untreated liquid flows through the precoat, an ion exchange reaction takes place, causing dissolved Impurities are removed from the liquid. In addition, undissolved impurities are removed from the untreated Liquid is removed by passing this liquid through the filter candles which are provided with a precoat layer 18 flows. A filter cake consisting of undissolved impurities builds up inside and on the precoat layer while the filtering phase continues. The cleaned liquid is - through the service line 48 - a storage container or fed to another facility.

The resins in the precoat may be exhausted and must be regenerated or removed. At this point in time the filter phase is interrupted by the valves 46 and 54 being closed. Then the filter canister 10 cleaned. To this end, the vent 26 and the drain valve 64 are opened and water, together with a purge gas, normally Air, introduced into the interior of the filter candles 18 at their lower end to advance the filter elements 18 tend to clean from the top to the bottom. The air is thereby introduced into the interior of the filter elements 18, that a valve 66 in the air line 68 connected to the outlet line 14 is opened. At the same time becomes water introduced into the filter elements 18 by opening a valve 74 in the backwash line 76. Under pressure

Air and backwash water enter the filtrate chamber 16 and flow upwards into the interior of the filter candles 18. Preferably the air flow throughput is between approx

• 2 _ ρ

0.3 to 0.6 standard no / min. u * ¹ ^ · Di FiIteroberflache while

the water throughput is about 20 l / min and m 'filter area. The drain valve 62 vrxrd controlled so that the water level drops slowly, preferably at one rate

909846/0707 / 20

from about 25 to 38 cm / min. The air and water that are in enter the filter container, therefore tend to flow through the upper portion of the filter candles 18 and first to remove the precoat there.

After the filter container 10 has run empty, the drain valve 64 closed and the container 10 fills again with liquid that flows in the opposite direction through the Filter candles 18 flows. After the container 10 to a height of about 15 cm above the tops of the filter candles 18 is filled, the valves 66, 74 and 76 are closed and the backwashing water is turned off by opening the valve 64 the container 10 removed.

The drain valve 64 is closed and the filter candles 18 are grounded again by opening the valves 66 and 74 in the air line 68 or in the backwash line 76 · backwashed. During this step, a slightly higher liquid throughput is used worked, namely with about 40 to 80 l / min and m filter area. Air is also used with a throughput of about 0.45 standard m ^ / min and m filter area supplied. After this the container 10 is filled to a level above the tops of the filter candles 18, the drain valve 64 is again opened so that the liquid level at a speed can drop from about 25 to 38 cm / min while the introduction of air and backwash fluid continues. The backwash valve 74 is closed and the evacuation is carried out with simultaneous supply of only air during a short Period of time continued to ensure complete drainage. After the container 10 is empty, ground the drain valve 64 and the air valve 66 closed. The backwash valve 74 is opened and the container becomes the third Times filled. After filling the container '10 v / ground the vent 26 and the valve 74 of the backwash line closed. The container 10 is filled with water and the filter candles 18 can now be provided with a precoat layer again as described above.

909846/0707

Although air was mentioned above as the cleaning gas, other gases can also be used for cleaning, such as for example nitrogen, oxygen and the like. However, air is most economical and readily available in most facilities. Other liquids can also be used in a corresponding manner can be used as water during the backwash phase. For example, alcohols and carbon tetrachloride are used as rinsing liquids and detergents and soap solutions in Consideration. The liquids are preferably supplied at a temperature in the range from about 38 to 93.degree.

Typical solid cation exchange resin particles which can be used in the specific filtering method described above are of the divenyrbenzene-styrene copolymer type, the acrylic type, the sulfonated carbon type, and the phenol type. These can be used, for example, in sodium, hydrogen or ammonium form. Typical solid anion exchange resin particles that can be used are phenol-formaldehyde-type, divinylbenzene-styrene copolymer'iTTp, acrylic-type, epoxy - type. The anion resin particles can, for example, in the. Hydr, o3cidform or in the chloride form can be used. Suitable resins are commercially available in large-grain form under the trade names Aberlite IR-120 and Aberlite IRA-400 from Röhm and Haas Company and Dowex-HCR-S and Dowex SBR-P from Dow Chemical Company. The finely divided synthetic resins are produced by reducing the grain size range through particle size reduction. These synthetic resin particles are regenerated and washed before they are used.

The following examples are intended - without limiting the range of the invention - show applications for the invention.

9Ö9846 / 0707

ouch

Example I.

The bubble point pressure was measured in the case of pilter candles with an outer layer of a mesh fabric made of stainless steel wire 165 × 800 and in the case of a filter candle with an outer layer in the form of a jacket provided with slits. The slot dimensions were 30 430 µm. When used as a filter layer, both the 165 x 800 stalildr ahtma's fabric and the jacket with 30 χ 4θ / µm slits have an absolute particle retention of about 30 / µm.

The bubble point tests were (ARP-901) carried out according to the aforementioned method, wherein the measuring values corresponding to the recommendation (ARP-901) were corrected to the Standardblas enpunktdruck for each filter candle, based on isopropanol at 25 ⁰ C to obtain. These values, based on isopr'opanol at 25 ° C., for the standard bubble point were 175 mm water column for the 165 x 800 wire mesh fabric and for the filter candle provided with the slit jacket with 30 "430 / µm slots 107 mm viasser column.

Accordingly, the filter candle had the slits Outer jacket has a lower bubble point pressure than the known filter candle, the same absolute particle retention capacity being present in both cases. These Reducing the bubble point pressure enables a greater one Amount of air the escape through the filter candle according to the invention during the precoat phase and during the filter phase in comparison to the conditions in the known filter candles.

909846/0707

Example II

Sine filter candle with a 165 x 000 wire mesh was made investigated in a test facility in connection with the alluviation of filter aids on the filter surface. After filling and precoating, the filter candle remained on a length of because of the gas inclusion at its upper end about 23 cm without precoat. With regard to the according to Example I values for the bubble point pressure obtained when using a filter candle with. a slot of 30 χ 430 / .mu.m cladding as the outer layer with a smaller one Gas inclusionG than with the filter candle ■ with the wire mesh to be expected, but a certain amount of gas inclusion would still be possible. have been expected with the consequence that a section

the filter candle also remains without a precoat. the Calculation based on the ratio of the bubble point pressures the slit jacket candle and the wire mesh candle result in a length of this alluvial-free area of about 14 cm.

When trying with a filter candle that had a slot of 30 430 / µm having jacket provided in accordance with the invention, it was found that the filter candle Could be provided with a precoat over its entire length, indicating that no gas was trapped was. Gas inclusions were dated by the invention Training already without the use of a - ^ ventilation ^ - sleeve or other cover part avoided.

According to the description above, a precoat layer is used in connection with the filter candle according to the invention used from finely divided ion exchange resin particles, but the invention is also advantageous when the Precoat layer consists of kieselguhr, cellulose fibers, polyacrylonitrile fibers or another filter aid, as is readily apparent to those skilled in the art.

909846/0707

Claims (8)

DR.-III. FRANZ TFUESTHOFF PATENT Attorneys _{dr pmL fr £ da WÜESTHOPF} WUESTHOFF-v. PECHMANN-BEHRENS-GOETZ dipping, gkhard puls (i _9J2 - _I97 i) DIPL.-CHEM. DR. E. FREIHERR VOK PECHMANN PROFESSIONAL REPRESENTATIVES BEFORE THE EUROPEAN PATENT OFFICE DR.-ING. DIETER BEHRENS MANDATAIRES AGREES PRES l'OFFICE EUROPEEN DES BREVETS DIPL.-ING.J DIPL.-WIRTSCH.-ING. RUPERT GOETZ D-8000 MUNICH 90 SCHWEIGERSTRASSE 2 phone: (089) 66 20 ji telegram: protectpatent telex: j 24 070 1Δ-52 038 Patent claims: Filter candle for vertical arrangement in a filter container with connection of a feed chamber formed in the container and a filtrate chamber using a precoat layer of filter aids, in particular ion exchange resin particles in a grain size range of less than 400 / µm, on the filter candle surface, ordering from one porous tubular core and an outer filter candle layer to support the precoat layer, characterized in that the outer layer of the Filter candle (18) at least at its upper end by a discontinuous slot (88) of elongated shape having jacket (86,96,98) is formed. 2. Filter candle according to claim 1, characterized in that the width of each slot (88) up to about 30 / µm and the length of each slot (88) is between about 45 and 430 / uni. 3. Filter candle according to claim 1 or 2, characterized in that the filter candle (18) has a absolute particle retention capacity * less than 50 µm and that the length of each slot (88) is at least about one and a half times the slot width. / 2 903846/0707 4. Filter candle according to one of claims 1 to 3 »thereby characterized in that the filter candle (18) an absolute particle retention capacity of less than about 30 µm and a bubble point pressure of less than about 175 mm water column. 5. Filter candle according to one of claims 1 to 4, characterized in that the porous tubular The core (82) is surrounded by a coarse screen mesh (84), which in turn is surrounded by the jacket, which has the slots (88) (86) and is connected to it by diffusion adhesion. 6 ". Filter candle according to one of Claims 1 to 4, characterized in that the filter candle (18) has a fine-meshed outer layer (102) to support the precoat layer, the outer layer (102) in the Distance from the upper end of the filter candle ends, and that the dumbbell (96) provided with the slots (88) when the band-shaped Training encloses only the upper end of the filter candle (18) free from the fine meshwork (102) and with the fine mesh (102) (at B) is sealingly connected. 7. Filter candle according to claim 6, characterized in that the one provided with slots (88) Sheath (96) enclosing and connected to this Ventilation sleeve (90) is provided, which has at least one vent opening (92) which extends from the jacket (96) is covered. 8. Filter candle according to one of claims 1 to 4, characterized in that a fine-meshed screen mesh (102) is provided on the outside of the filter candle (18) to support the precoat layer, this fine-meshed braid at a distance from the upper end of the filter candle that ends the upper end of the filter candle (18) from a ventilation sleeve (90) is enclosed, which (at C) with / 3 9 09 8 4 6/0707 _ 3 - the upper end of the fine-meshed screen mesh (102) is sealingly connected, and that the ventilation sleeve (90) has at least one vent opening (92), which is separated from the one provided with the slots (88), possibly only is still covered as a narrow disk jacket (98). 90 98 4 6/070?